Methylene chloride stabilized with ketones

ABSTRACT

Ketones and optionally epoxides in admixture with methylene chloride have been found to prevent degradation of methylene chloride in the presence of metals, metal halides, combinations thereof, and aromatic compounds, which react with methylene chloride in the presence of said metals, metal halides and combinations thereof. Reactions of aliphatic organic compounds with said metals, metal halides and combinations thereof to form products which result in deterioration of methylene chloride are also inhibited. A method for vapor degreasing metals by using the stabilized methylene chloride is described.

United States ?atent 1 Beckers Dec. 2, 1975 METHYLENE CHLORIDE STABILIZED WITH KETONES [75] Inventor: Norman L. Beckers, Chardon, Ohio [73] Assignee: Diamond Shamrock Corporation,

Cleveland, Ohio 22 Filed: Feb. 23, 1973 21 Appl. No.: 334,985

[44] Published under the Trial Voluntary Protest Program on January 28, 1975 as document no.

3,406,213 10/1968 Patron 260/6525 R 3,423,476 l/l969 Patron R 3,535,392 10/1970 Cormany ct a1. R 3,546,304 12/1970 Patron 260/6525 R Primary ExaminerHoward T. Mars Attorney, Agent, or FirmWilliam A. Skinner [57] ABSTRACT Ketones and optionally epoxides in admixture with methylene chloride have been found to prevent degradation of methylene chloride in the presence of metals, metal halides, combinations thereof, and aromatic compounds, which react with methylene chloride in the presence of said metals, metal halides and combinations thereof. Reactions of aliphatic organic compounds with said metals, metal halides and combinations thereof to form products which result in deterioration of methylene chloride are also inhibited. A method for vapor degreasing metals by using the stabilized methylene chloride is described.

2 Claims, No Drawings METHYLENE CHLORIDE STABILIZED WITH KETONES BACKGROUND OF THE INVENTION Methylene chloride is a highly versatile and useful solvent for various industrial applications at both normal and elevated temperatures A particularly important industrial use is the vapor degreasing of metals. Methylene chloride is known to be more stable than other chlorinated hydrocarbons solvents such as perchloroethylene, trichloroethylene and methyl chloroform when the solvents are used in unstabilized condition. For example, methylene chloride is more resistant to oxidation, hydrolysis and pyrolysis than other chlorinated solvents and does not substantially react with aluminum in the aluminum scratch test commonly used to indicate unstabilized or minimally stabilized methyl chloroform. In addition, methylene chloride may be used to greater advantage in vapor degreasing of metals than other known degreasing solvents since it may be used effectively at lower temperatures due to its lower boiling point and excellent stability. Methylene chloride is particularly desirable for such degreasing operations since it is substantially resistant to photochemical activity and therefore does not contribute to air pollution by smog formation. However, methylene chloride when used in various metal cleaning functions, including vapor degreasing, suffers the disadvantage of being reactive with aromatic compounds in the presence of metals, metal halides and combinations thereof, including aluminum, zinc and iron, halides thereof, and combinations of said metals and halides which react with the methylene chloride to produce hydrochloric acid and objectionable high boiling tarry substances which render the methylene chloride unsuitable for further use. The entire reaction of methylene chloride in the presence of aromatic compounds is not completely understood but is believed to be a condensation reaction catalyzed by metal, metal halides or combinations thereof. Thus, the aromatic compound reaction with methylene chloride is believed to be catalyzed, or initiated and catalyzed by the presence of metals such as aluminum, zinc, iron and the like, halides of said metals and combinations of said metals and halides. Such reactions are thought to be of the nature of a Friedel- Craft type reaction. Methylene chloride also disadvan tageously suffers degradation by reaction of aliphatic organic compounds such as transdichloroethylene, 1,1,l-trichloroethane and carbon tetrachloride with said metals, metal halides and combinations thereof. The reaction products are colored tar-like masses which render the methylene chloride unsuitable for use as a solvent, particularly in vapor degreasing of metals. Aromatic and aliphatic organic compounds of this nature and metals such as aluminum, iron and zinc, their halides and combinations are generally introduced into the methylene chloride from various cutting oils and lubricants used in metal fabricating operations which are carried over into the methylene chloride solvent during vapor degreasing or other cleaning of the fabricated metal parts. Solvent manufacturing, handling and storage equipment is another source for introduction of such impurities. To prevent degradation and other types of deterioration such as oxidation, hydrolysis and pyrolysis which may occur in some instances, it has been the practice to incorporate minor quantities of various organic compounds into methylene chloride,

which compounds act as stabilizers to substantially prevent such degradation. It is desirable to provide methylene chloride stabilized to effectively prevent degradation in various applications, and the demand still exists for a low cost stabilized methylene chloride composition that can be easily prepared and which provides optimum stabilization under many different operating conditions.

SUMMARY OF THE INVENTION An object of this invention is to prevent deterioration or degradation of methylene chloride in association with metals, metal halides and combinations including aluminum and/or aluminum chloride, and an aromatic compound capable of reacting with methylene chloride in the presence of said metals, metal halides and combinations.

Another object of this invention is to prevent deterioration or degradation of methylene chloride in association with metals, metal halides and combinations including aluminum, iron and zinc, halides of said metals and an aliphatic organic compound capable of reacting with these metals, metal halides and combinations thereof in the presence of methylene chloride.

A further object of this invention is to provide a stabilized methylene chloride composition in which the stabilizers are low in cost and capable of being incorporated with ease into the methylene chloride.

A still further object of this invention is to provide a process for the degreasing of metals by contacting the metals with methylene chloride stabilized to prevent degradation of the methylene chloride in the presence of metals, metal halides and combinations thereof including aluminum, iron and zinc, halides of said metals and combinations and aromatic compounds which react with the methylene chloride in the presence of said metals, metal halides and combinations thereof.

Still another object of this invention is to provide a process for the degreasing of metals by contacting the metals with methylene chloride stabilized to prevent degradation of the methylene chloride in the presence of an aliphatic organic compound which reacts with metals including aluminum, iron, zinc and the like, halides of said metals and combinations of the individual metals and salts thereof.

These and additional objects of the present invention will become apparent to those skilled in the art from the description and claims which follow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The objects set forth above have been found to be attained by providing a composition consisting essentially of methylene chloride containing stabilizing amounts of from about 0.05 to about 2.0 percent by weight of the methylene chloride of methyl ethyl ketone, acetone, and acetone optionally combined with propylene oxide.

The quantity of the stabilizing agents useful in the practice of this invention will vary depending upon the conditions of use, the identity and quantity of other stabilizers incorporated into the methylene chloride and other practical operating considerations. Each stabilizing agent or compound may generally be used within the range of from about 0.05 to about 2.0 percent and preferably from about 0.10 to about 1.0 percent by weight of the methylene chloride. Although higher concentrations may be used, if desired, no additional benefit is obtained and the cost is unnecessarily increased. While the above composition containing stabilizing agents provides optimum prevention of degradation of the methylene chloride under a variety of operating conditions it is also possible to stabilize methylene chloride by deleting the propylene oxide depending on the stabilization required for the practicular operating condition.

The stabilized composition may be used for the degreasing of metals by contacting the metals with the stabilized composition. It is also possible to use the stabilized methylene chloride composition for degreasing metals by deleting the propylene oxide. Thus, the process for vapor degreasing metals comprises contacting the metals to be degreased with the above described stabilized methylene chloride compositions wherein the methylene chloride contains stabilizing amounts of methyl ethyl ketone, acetone only, or an admixture of acetone and propylene oxide.

In degreasing metals with the above described preferred stabilized methylene chloride in the presence of an aromatic compound which reacts with methylene chloride in the presence of metals, metal halides and combinations thereof including aluminum, iron, zinc, halides of said metals and combinations, there exists upon contact of the metal with the stabilized methylene chloride a composition comprising methylene chloride, a stabilizing amount of from about 0.05 to about 2.0 weight percent of the methylene chloride of methyl ethyl ketone, or acetone only or acetone optionally combined with from 0.05 to about 2.0 percent by weight of propylene oxide, and an organic compound which reacts with methylene chloride in the presence of said metals, metal halides and combinations. The metals, metal halides and combinations may be present from any source such as chloride formed by drilling or other machining of aluminum or aluminum-containing materials with various working fluids such as cutting oils, lubricants and the like, or aluminum chloride may be present from the reaction of methylene chloride 4 with aluminum. The reactive aromatic compounds include toluene, mesitylene, naphthalene, and the like. The reaction of methylene chloride in the presence of aliphatic organic compounds such as trans-dichloroethylene, carbon tetrachloride and 1,1 ,l-trichloroethane, metals, metal halides and combinations may also be inhibited by methylene chloride stabilized with the same above-noted amounts of methyl ethyl ketone, acetone only or acetone optionally combined with propylene oxide.

In order that those skilled in the art may readily understand the present invention and certain specific embodiments by which it may be carried into effect the following illustrative examples are presented.

2 In Example 1 of Table I, ml of substantially water 30 in the appearance of the solvent, the pH or the aluminum in the vial. Toluene in an amount of Spercent by volume and about 0.04 grams of anhydrous aluminum chloride were then added to the vial, the contents stirred, changes in the contents recorded, and the vial loosely capped and allowed to stand. After 4 hours and after 22 hours changes in the appearance of the aluminum coupons and the solvents, and relative pH values of the solvents, were recorded. The procedure of Example l was followed in Examples 2 to 8 of Table I. In

Examples 2 and 3, acetone and methyl ethyl ketone stabilizers were respectively added to the methylene chloride. In Examples 4 to 8 various compounds reported in the prior literature to be useful in stabilizing chlorinated solvents were evaluated for their ability to stabilize methylene chloride. In Examples 4 to 8 after the tightly capped vials had been standing for l6 hours no changes had occurred in the appearance of the solvent, the pH or the aluminum coupons. The results of the tests of Examples 1 to 8 are set forth in Table I.

TABLE I INHIBITION OF REACTION OF AROMATIC COMPOUNDS WITH METHYLENE CHLORIDE Upon Addition of 5% Vol. Toluene Example Solvent and 0.04 grams After After No. System Aluminum Chloride 4 Hours 22 Hours l Methylene Chloride Light Yellow Precipitate Dark Orange No Change Containing Solution Colorless pH 3 Aluminum Coupon HCl fumes 2 Methylene Chloride Very Slight Whitc Very Slight White Containing Preeipitatc Light Yellow Precipitate Aluminum Coupon Solution Colorless Preeipitate. Solution Stabilized With Solution Colorless 2.8 Wt. 71 Acetone Colorless pH about 5.0

pH about 4.5 3 Methylene Chloride Very Slight White Very Light No Change Containing Precipitate Gray Prccipitate Aluminum Coupon Solution Colorless Solution Colorless Stabilized With pH about 4.8 1.7 Wt. 71 Methyl Ethyl Ketone 4 Methylene Chloride Solution Light Brown Solution Light Gray No Change Containing Purple Tan Aluminum Coupon Preeipitate Brown Spots on Stabilized With Turned purple-brown Aluminum Coupon 2.8 Wt. 71 after a few minutes Grey-white Precipitate Dimcthoxymethane pH 3 5 Methylene Chloride Solution Dark Purple Solution Black Containing Colored Purple-Black Precipitate Aluminum Coupon and Precipitate Solution Stabilized With Present Yellow- 0.7 Wt. 7( pH about 3.5 Green Methyl Butynol pH about 4.5 6 Methylene Chloride Light Lavender Solution pH about Containing Preeipitate Dark Gray 4.5

Aluminum Coupon And Prccipitate TABLE l-continued INHIBITION OF REACTION OF AROMATIC COMPOUNDS WITH METHYLENE CHLORIDE Upon Addition of 5% Vol. Toluene Example Solvent and 0.04 grams After After No. System Aluminum Chloride 4 Hours 22 Hours Stabilized With Present 2.8 Wt. 91 pH about 3 l. l -Dimethoxyethane 7 Methylene Chloride Yellow Green Yellow precipitate White Containing Precipitate On Aluminum Precipitate Aluminum Coupon Coupon Solution Stabilized With Solution Green- Yellow Wtf/1 Gray pH about 1.3-Dioxolane pH About 3.5 4.5 8 Methylene Chloride Red Precipitate Orange precipitate Pink-Brown Containing On Aluminum Coupon Precipitate Aluminum Coupon Solution Colorless Solution Stabilized With pH about 4.0 Colorless 0.8 Wt. 71 pH about 4.5 l.-l-Dioxane From Table I it will be readily observed that after four hours the methylene chloride without the ketone stabilizers had undergone a degradation reaction resulting in a dark orange coloration, evolvement of hydrogen chloride gas and complete loss of utility of the solvent. In Examples 2 and 3 the acetone and methyl ethyl ketone, respectively, prevented degradation of the system by reaction of the methylene chloride and toluene. Examples 4 to 8 inclusive of Table I show that various compounds frequently used as solvent stabilizers are not as effective as acetone or methyl ethyl ketone in inhibiting degradation of methylene chloride by reaction of aromatic compounds with methylene chloride in the presence of metals, metal salts and combinations thereof.

In Examples 9 to 1 l of Table II, below, an aluminum reflux stability test was carried out by placing 190 ml of substantially water-free mehtylene chloride and 5 percent by volume (IO ml) of a commercially available stabilized vapor degreasing grade l,l,l-trichloroethane in a flat bottom 300 ml boiling flask fitted with a condenser. One strip of aluminum about 1 /2 X9 cm was suspended in the condenser. About one gram of 20 mesh aluminum was added to the flask. In Examples 10 the aqueous phase following extraction of the solvent with an equal volume of neutral distilled water and after the system was refluxed for varying time periods.

The results of the various tests are shown in Table II below.

In Example 9 of Table II deterioration of the solvent system occurred due to the reaction of aluminum with the contained 1,] ,l-trichloroethane. In Examples 10 and II of Table II the addition of acetone and methyl ethyl ketone to the solvent system prevented such deterioration.

The inhibition of the degradation of methylene chloride by the reaction between 1.1 ,l-trichloroethane and aluminum and metal salts by acetone and methyl ethyl ketone is especially surprising and unexpected when it is realized that the stabilizers included in the commercial vapor degreasing grade l,l,1-trichloroethane to prevent reaction of the l,l,1-trichloroethane with metals and/or metal salts in the presence of chlorinated solvents failed to inhibit the degradation of the methylene chloride. Only when the acetone and methyl ethyl ketone were respectively, admixed with the methylene chloride containing the stabilized 1,1 l-trichloroethane was degradation of the methylene chloride prevented.

TABLE II EFFECT OF ALIPHATIC ORGANIC COMPOUNDS ON ALUMINUM REFLUX STABILITY TESTS OF METHYLENE CHLORIDE *Determined by visual observation and l 1 0.25 Wt. percent of acetone and 0.25 Wt. percent of methyl ethyl ketone were respectively added to the methylene chloride. The methylene chloride solvent systems were refluxed for a varying period of days. During the extended period of reflux the solvent vapor surrounded, condensed, and dripped from the suspended strip onto the other partially immersed strip. The pH and acid content, as HCI, were determined on In Examples 12 to 18 of Table III, below, the aluminum reflux stability tests consisted of placing 200ml of methylene chloride in a 300 ml flask, adding about 0.5 grams of 20 mesh aluminum and suspending a bright aluminum coupon about 2 X 7 cm. in a condenser fitted to the flask. Methylene chloride and the solvent eontaining durehe lnesitylene and comblll'gltlohs 0f mes'ttylene with methyl ethyl ketone only, with aeeterie aria 7 propylene oxide and with only acetone were refluxed for varying time periods. In all the tests the pH and acid content. as HCl, were determined and visual observation of the aluminum condenser coupon were made at 8 minations were made with a portion of the water-layer obtained by extraction of the solvent with water equal to the volume of the solvent system.

Although the present invention has been described the completion of the test. The results of these tests are 5 with detailed reference to specific embodiments set forth in Table III below. thereof, it is not intended to be so limited since modifi- Table III illustrates the prevention of degradation of cations and alterations therein may be made which are methylene chloride by methyl ethyl ketone in the preswithin the complete intended scope of this invention as ence of aluminum and aluminum chloride and the arodefined by the appended claims.

TABLE III EFFECT OF AROMATIC COMPOUNDS ON ALUMINUM REFLUX STABILITY TESTS WlTH METHYLENE CHLORIDE Example Days Acid as Color Condenser No. Solvent System Volume.-Additi\'e Test pH ppm HCI Solvent Coupon Corrosion l2 Methylene Chloride 3 7.0 None Clear and Blisters colorless l3 Methylene Chloride Mcsitylene 5 3 HCl Orange- General (Trimethyl Benzene) Fumes Black Severe l4 Methylene Chloride 59 Mesitylene 14 TI None Clear and None 0.25 wt. '71 of colorless Methyl Ethyl Ketone l5 Methylene Chloride 571 Mesitylene Z8 7.0 None Clear. gray None 0.25 1.9? Acetone 0.50 \\'t./: Propylene oxide l6 Methylene Chloride 5% Mesitylene 22 7.3 None Clear. light None 0.25 wt "/1 Acetone gray 0.25 \\'t. '71 Propylene Oxide 0125 \\'t./( Butylenc Oxide l7 Methylene Chloride 571 Durene (Tetra- 5 Pink Purple methyl Benzene) Blisters 18 Example 17 after one 5% Durene 6 5.4 108 Yellow. General additional day of turbid Severe What is claimed is:

l. A stabilized methylene chloride composition consisting essentially of methylene chloride and stabilizing amounts of from about 0.05 to about 210 percent by weight of the methylene chloride of a compound selected from the group consisting of methyl ethyl ketone and acetone.

2. The composition of claim 1 wherein the compound is from about 0.1 to about 1.0 percent by weight of the 

1. A STABILIZED METHYLENE CHLORIDE COMPOSITION CONSISTING ESSENTIALLY OF METHYLENE CHLORIDE AND STABILIZING AMOUNTS OF FROM ABOUT 0.05 TO 2.0 PERCENT BY WEIGHT OF THE METHYLLENE CHLORIDE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF METHYL ETHYL KETONE AND ACETONE.
 2. The composition of claim 1 wherein the compound is from about 0.1 to about 1.0 percent by weight of the methylene chloride. 